Abstract

With the aim of verifying the age readings in whole otoliths of cardinalfish Epigonus crassicaudus, two readers conducted independently three readings, with an elapsed time of 15 days among readings, of the annular structure of otoliths from 96 fish with length ranging between 20 and 37 cm. In addition, the age readings in whole otoliths were compared with readings on thin transverse sections, recording also the frequency of the most marked secondary rings. Finally, the growth parameters in length of the von Bertalanffy growth function (VBGF) were estimated by admitting ageing error. A nonlinear model with random effects (NLRE) was used, in which the error structure of the sampled age distribution is specified. The estimation of the growth parameters was compared with the performance of a standard nonlinear model (SNL) of estimation. The results showed that the annular structure in whole otoliths can be determined with high precision. Also there are not significant differences in the age determination between whole otoliths and thin transverse sections. In the last technique a higher frequency of secondary rings was counted than in whole otoliths. The estimates of growth parameters with NLRE were more consistent than those estimates obtained with the SNL model. It is concluded that the age readings in whole otoliths is determined with high precision, which is an easy technique to be implemented for monitoring the age structure of cardinalfish. It was confirmed that the growth in length of the VBGF for cardinalfish is represented by an asymptotic length close to 45 cm of total length and a growth coefficient ranging between 0.16-0.18 yr-1.